ANTENNA AND ELECTRONIC DEVICE
A small-sized normal mode helical antenna is provided that is not affected by nearby conductors. The antenna is an antenna including a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near the coil center.
The present technology relates to an antenna and an electronic device.
BACKGROUND ARTConventionally, a helical antenna having a configuration in which a conductive wire is wound spirally has been known. The helical antenna has a structure capable of downsizing an antenna. Furthermore, in a case where a peripheral length of a single winding of the helical antenna is sufficiently smaller than a wavelength, radiation occurs in a direction perpendicular to an axis of the helical antenna. The helical antenna having such characteristics is referred to as a normal mode helical antenna. The normal mode helical antenna is a small and highly efficient antenna.
Patent Document 1 describes a technique in which a coil cross-sectional area S, a pitch p, and a total length of the normal mode helical antenna are all 1/10 or less of a wavelength λ, and the coil cross-sectional area S and the pitch p satisfy a relationship of (2πS≈pλ) with respect to the wavelength λ, so that the normal mode helical antenna can be used even in an environment near a dielectric/metal part or a human body.
Patent Document 2 describes a configuration of a monopole type helical antenna having an element with a wire, the one end of which is grounded and another end of which is opened, being spirally wounded around the element, in which a winding diameter of the wire increases from a ground side toward an open side.
CITATION LIST Patent Document
- Patent Document 1: JP 2005-354297 A
- Patent Document 2: JP 2003-324795 A
As one of the problems, since the normal mode helical antenna described in Patent Document 1 has radiation due to the same principle as that in a dipole antenna and an inverted-F antenna, radiation power decreases when a metal or a human body is nearby, and sufficient efficiency cannot be secured in a case where the normal mode helical antenna is incorporated into an electronic device. Furthermore, another problem is that due to its cylindrical coil shape, the normal mode helical antenna occupies a large area in the electronic device. The helical antenna described in Patent Document 2 improves radiation characteristics, and the improvement is different from reduction of influence by the metal and the human body and downsizing that are one of the objects of the present technology.
An object of the present technology is to provide an antenna and an electronic device capable of reducing influence of a metal and a human body and downsizing.
Solution to ProblemsThe present technology is, for example, an antenna including a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near a center of the coil.
Furthermore, the present technology is an electronic device on which such an antenna is mounted.
The embodiments described below are preferable specific examples of the present technology, and various technically suitable limitations are given to the embodiments. However, the scope of the present technology is not limited to these embodiments unless there is a description to particularly limit the present technology in the following description. Furthermore, in the following description, the same names and reference numerals indicate the same or equivalent constituent elements, and redundant description will be omitted as appropriate.
As illustrated in
As illustrated in
When the separation distance D from the copper plate 4 decreases, the decrease in the radiation power of the component of the electric current is larger than the decrease in the radiation power of the component of the magnetic current. The same influence is generated by a human body, which is a conductor similarly to the copper plate 4. In order to prevent degradation of the performance of the antenna due to a conductor, it is effective to increase the component of the magnetic current.
As illustrated in
As illustrated in
As illustrated in
In Table 1, the area is an area occupied by an outer shape of the normal mode helical antenna projected on a two-dimensional plane (for example, the (x-y) plane). In a case of the conventional technology, the outer shape is a rectangle, and in a case of the present technology, both ends of the rectangle have a tapered outer shape. The volume is a volume of a three-dimensional body formed by connecting outer sides of a plurality of coils. As can be seen from Table 1, the present technology can decrease the area and the volume as compared to the conventional technology, and a gain of an electric current component decreases, but a gain of a magnetic current component increases. Therefore, the present technology can increase the radiation originating from the magnetic current as compared to the conventional technology, and can prevent the degradation of the performance of the antenna in the environment near the metal part in the electronic device or the human body.
Hereinafter, a plurality of embodiments and application examples of the present technology will be described in order. Note that in the drawings of the embodiments described below, the feeding points are omitted. A position of the feeding point illustrated in
An area of a cross section perpendicular to an axis of a coil for a single turn at each end of the coil constituting a normal mode helical antenna described in the following plurality of embodiments is less than an area of a cross section perpendicular to the axis of the coil near the coil center.
A wristband-type activity tracker as an example of the wearable device is also called a smart band, and can acquire and display data related to human activities such as the number of steps, a moving distance, calorie consumption, an amount of sleep, and a heart rate only by being wound around an arm. Moreover, the acquired data can be managed by a smartphone. Moreover, a mail transmission/reception function can be included. The antenna 17 is used for these communication functions.
Note that the present technology can be applied not only to wireless earphones and wearable devices but also to another electronic devices. For example, the present technology can be applied to a wireless controller of a game machine, an IoT device, an audio-visual device such as a digital camera, a radio, a speaker, and a recorder, a head-mounted display, smart glasses, a smartphone, and the like.
Therefore, by increasing a coil diameter (coil sectional area) near the coil center compared to a coil diameter (coil sectional area) at each end, the magnetic current intensity is increased, and it makes it possible to use the above-described present technology in an environment near a metal part in an electronic device or a human body. Furthermore, since the contribution from near the coil end to the magnetic current is small, by reducing the coil diameter near the coil end, an occupied area in the electronic device can be reduced.
Although the embodiments of the present technology have been specifically described above, the present technology is not limited to each of the above-described embodiments, and various modifications based on the technical idea of the present technology can be made.
In the above-described embodiments, in a case where there is a plurality of coils, the diameters of some coils may be smaller or larger than the diameter of another coil. For example, in a normal mode helical antenna having a plurality of coils, at least one coil in coils without feeding points may be thicker than a coil with a feeding point.
Furthermore, one or a plurality of arbitrarily selected aspects of the modifications can be appropriately combined. Furthermore, the configurations, the methods, the steps, the shapes, the materials, the numerical values, and the like of the above-described embodiments can be combined with each other without departing from the gist of the present technology.
Note that the present technology can also have the following configurations.
-
- (1)
- An antenna, including
- a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near a center of the coil.
- (2)
- The antenna according to (1), including
- a feeding point near the coil center.
- (3)
- The antenna according to (1) or (2), in which
- the area of the cross section perpendicular to the axis of the coil monotonously decreases from near the coil center toward both ends.
- (4)
- The antenna according to any one of (1) to (3), in which
- a pitch of the coil is not constant.
- (5)
- The antenna according to any one of (1) to (4), in which
- a shape projected on a cross section perpendicular to the axis of the coil is a convex shape.
- (6)
- The antenna according to (1), including two or more coils, and having an impedance matching mechanism in which both ends of one coil are short-circuited to both ends of another coil.
- (7)
- The antenna according to (6), in which
- at least one of coils without feeding points is thicker than a coil to which the feeding point is connected.
- (8)
- The antenna according to (1), including
- an impedance matching mechanism provided with a coil and a feeding tap both ends of which are short-circuited.
- (9)
- The antenna according to (1), including two or more coils having substantially equal shapes, in which
- the coils are arranged in plane symmetry, the antenna being configured such that both ends of the coils are short-circuited.
- (10)
- The antenna according to (1), including patterns on both surfaces of a dielectric material and through holes penetrating the dielectric material, in which
- the coil is formed by connecting the patterns on both surfaces via the through holes.
- (11)
- The antenna according to (1), in which
- the coil is formed by a pattern on a surface of a dielectric material.
- (12)
- The antenna according to (1), in which
- a shape of the coil is formed by a good conductor disposed around a magnetic material.
- (13)
- The antenna according to (1), further including
- a good conductor at a position substantially parallel to the axis of the coil.
- (14)
- An electronic device, including an antenna including
- a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near a center of the coil, in which
- the axis of the coil is substantially parallel to a metal part in the device and/or a human body when wearing the antenna.
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- 6, 6A, 6B, 6C, 6D, 17, 20 normal mode helical antenna
- 7, 8, 9, 10, 11, 12, 13 coil
- 23 metal plate
- 24 substrate
Claims
1. An antenna, comprising
- a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near a center of the coil.
2. The antenna according to claim 1, including
- a feeding point near the coil center.
3. The antenna according to claim 1, wherein
- the area of the cross section perpendicular to the axis of the coil monotonously decreases from near the coil center toward both ends.
4. The antenna according to claim 1, wherein
- a pitch of the coil is not constant.
5. The antenna according to claim 1, wherein
- a shape projected on a cross section perpendicular to the axis of the coil is a convex shape.
6. The antenna according to claim 1, comprising two or more coils, and having an impedance matching mechanism in which both ends of one coil are short-circuited to both ends of another coil.
7. The antenna according to claim 6, wherein
- at least one of coils without feeding points is thicker than a coil to which the feeding point is connected.
8. The antenna according to claim 1 comprising
- an impedance matching mechanism provided with a coil and a feeding tap both ends of which are short-circuited.
9. The antenna according to claim 1, comprising two or more coils having substantially equal shapes, wherein
- the coils are arranged in plane symmetry, the antenna being configured such that both ends of the coils are short-circuited.
10. The antenna according to claim 1, comprising patterns on both surfaces of a dielectric material and through holes penetrating the dielectric material, wherein
- the coil is formed by connecting the patterns on both surfaces via the through holes.
11. The antenna according to claim 1, wherein
- the coil is formed by a pattern on a surface of a dielectric material.
12. The antenna according to claim 1, wherein
- a shape of the coil is formed by a good conductor disposed around a magnetic material.
13. The antenna according to claim 1, further comprising
- a good conductor at a position substantially parallel to the axis of the coil.
14. An electronic device, comprising
- an antenna including a coil constituting a normal mode helical antenna, an area of a cross section perpendicular to an axis of the coil for a single turn at each end of the coil being less than an area of a cross section perpendicular to the axis of the coil near a center of the coil, wherein
- the axis of the coil is substantially parallel to a metal part in the device and/or a human body when wearing the antenna.
Type: Application
Filed: Aug 17, 2021
Publication Date: Oct 12, 2023
Inventors: YUKIO KANEKO (TOKYO), TAKASHI KAWAMURA (TOKYO), TETSUO IKEDA (TOKYO)
Application Number: 18/042,496